The present invention is related to a digital camera, and more specifically, directed to a high speed image selecting method and a digital camera equipped with a high speed image selecting function, by which an enlarged thumbnail image is fed in fast-forward/fast-backward modes when an image is displayed on a display unit such as a liquid crystal display.
Very recently, digital cameras (electronic still image cameras) have been developed, and are commercially available, and thus are gradually popularized.
A digital camera is arranged as follows. Imaging (photographing) light is photoelectrically converted into image data, and this image data is recorded on a recording medium, and thereafter is outputted to an external image processing apparatus, for instance, a personal computer. Then, the image data is processed by way of a printing image data forming process in the external image processing apparatus, and then the formed printing image data is outputted to a printer, so that a photographed image is printed/reproduced on a print paper.
It should be noted that the most digital cameras are equipped with liquid crystal displays (LCD) for displaying photographed images and the like. On the other hand, image data acquired by photoelectric converting operation are compression-processed to be recorded on recording media. Normally, the compression process operation is carried out based on the JPEG (Joint Photographic Image Coding Experts Group) standard (will be referred to as “JPEG compression” hereinafter).
In the case that an image is selected on the side of a personal computer, a plurality of thumbnail images are previously acquired to be displayed on a monitor, and a user selects a desirable image. Then, the selected image data is acquired from a digital camera to be expanded, and the expanded image is displayed on the monitor. After this expanded image is confirmed by the user, this image is processed by executing a color printing image data forming process, and then this processed image is printed out by a printer connected to the personal computer.
A thumbnail image corresponds to a compressed image which is used when a desirable image is selected from image data acquired by a personal computer and the like. Assuming now that a data size (namely memory capacity) of image data for 1 frame is equal to 1,024×768 pixels, a thumbnail image corresponding to this 1-frame image is such a compressed image having approximately 86×60 pixels by thinning image data from this 1-frame image data. Then the thumbnail image is recorded on a recording medium of a digital camera.
In such a system that a digital camera is connected to a communication line and a wireless (radio) unit such as a portable telephone so as to transmit desirable image data via either a wire line or a wireless line, and/or in order to directly transmit printing image data from the digital camera to a printer to be printed out, this system should be arranged in a manner that the images are reproduced on a liquid crystal display on the side of the digital camera so as to select a desirable image.
However, since the image data have been JPEG-compressed to be stored in the recording medium, these JPEG-compressed image data stored in this recording medium should be read out and then be expanded, and thereafter be extended over a frame memory in order to reproduce/display the images on the liquid crystal display.
When expanding means for compressed data is constituted by a hardware circuit, expanding/extending process time of these compressed data may be shortened. However, in popularized digital cameras, expanding means are normally arranged in a program form (will be referred to as an “expanding program” hereinafter) so as to reduce product cost. In such popularized digital cameras, 2 to 3 seconds are necessarily required to expand a 1-frame image (1,024×768 pixels) which has been JPEG-compressed by using this expanding program.
As a result, there is a problem that users have such feelings that image display time would be prolonged. Moreover, when a desirable image is selected, image data must be sequentially read out to be displayed. Under such a circumstance, if a desirable image is stored in a later order, then a long time duration is actually required in order to select this desirable image. Thus, there is a further problem that such a lengthy access time is practically inconvenient.